Self-hosted employee directory (in-app management + CSV import)

Most sites have no external HR database, so add a self-hosted directory mode.

- New employee_directory_mode setting: 'external' (default; read a separate HR
  DB, unchanged) or 'selfhosted' (app-owned table).
- DirectoryEmployee model + directoryemployees table (migration 7d16). to_dict
  emits the same keys the external contract uses (SSO/First_Name/...), so both
  modes share one response shape and the frontend is unchanged.
- Employee search / single / batch lookup branch on the mode.
- Self-hosted-only management endpoints: list, create, update, delete, and CSV
  import (upsert by SSO). Guarded so they only work in self-hosted mode.
- EmployeeDirectory.vue management page (Settings > Locations & Organization):
  table + search + pagination, add/edit/delete, CSV import (file or paste).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/employees/plugin.py

@@ -16,6 +16,7 @@ from flask import Flask, Blueprint
 from shopdb.plugins.base import BasePlugin, PluginMeta
 
 from .api import employees_bp
+from .models import DirectoryEmployee
 
 logger = logging.getLogger(__name__)
 
@@ -55,8 +56,9 @@ class EmployeesPlugin(BasePlugin):
         return employees_bp
 
     def get_models(self) -> List[Type]:
-        """No models - the directory is an external database."""
-        return []
+        """Self-hosted directory table (used when directory_mode=selfhosted).
+        External mode reads a separate DB via employee_connection instead."""
+        return [DirectoryEmployee]
 
     def get_config_schema(self) -> List[Dict]:
         """Employee directory DB connection. Host/name/user are settings the